The present disclosure relates generally to the field of methods and apparatus for measurement, testing, and evaluation of residual stresses of various materials using, for example, indentation.
Various types of systems for measuring material properties (e.g., hardness, residual stress, elastic modulus, etc.) are known in the art. Measurement of, for example, residual stress is an important consideration when designing devices.
For example, residual stresses can affect the mechanical performance (e.g., static and fatigue strength, fracture toughness, corrosion-/wear-resistance, etc.) and thus the reliability of components and devices. Residual stresses can be introduced by, for example, thermal mismatch or mechanical/thermal processing during the manufacturing, welding, and sintering operations. In a thin-film system, residual stresses have been generated from, for example, a thermal expansion mismatch between a film and a substrate during cooling in a deposition process. In welded metals, residual stresses have been caused by the welding thermal cycle due to heterogeneous heating and cooling. Residual stresses have resulted also from crystalline mismatches (e.g., face-centered cubic material in contact with body-centered cubic material, etc.).
Methods for the measurement of residual stresses have included mechanical stress-relaxation methods (e.g., hole drilling technique, saw cutting technique, curvature measurement method for a film/coding system, layer removal technique, etc.) and physical-parameter analysis methods (e.g., analysis of x-ray diffraction, ultrasonic wave, magnetic Barkhausen noise, neutron diffraction, and Raman spectra, etc.). However, mechanical stress-relaxation methods have been limited in application due to the destructive nature of the method. Physical-parameter analysis methods have been limited in application due to the requirement of the preparation of stress-free reference samples for comparison purposes. Moreover, physical methods have generally not been useful in determining residual stress of amorphous/glass materials that do not have a long-range ordered atomic structure. See, e.g., JANG, “Estimation of residual stress by instrumented indentation: A review,” Journal of Ceramic Processing Research, Vol. 10, No. 3, 391-400 (2009).
With instrumented indentation (e.g. nanoindentation, etc.), it has been possible to measure a variety of mechanical properties (e.g., hardness, Young's modulus, yield strength, work-hardening exponent, creep stress exponent, fracture toughness, and small-scale mechanical behavior, etc.) by analyzing the indentation load-displacement curve without the need to observe a hardness impression using microscopy.
Existing systems for measuring material properties such as residual stress, however, frequently require a zero-stress reference sample (which may be difficult to obtain), evaluation of indentation contact area, and/or separate expensive testing systems (e.g., microscopy, indentation, etc.).
Consequently, there remains a need in the material property measurement industry to efficiently measure residual stress and other properties without the requirement of a separately manufactured zero-stress reference sample. In particular, there remains a need for accurately, efficiently, and reproducibly measuring residual stresses of various materials.
Some publications discussing various aspects of measurement of residual stress and/or indentation include: BOCCIARELLI et al. “Indentation and imprint mapping method for identification of residual stresses,” Computational Materials Science 39 (2007) 381-392; FAISAL et al., “A Review of Patented Methodologies in Instrumented Indentation Residual Stress Measurements,” 2011, 4, 138-152; JANG et al., “Assessing welding residual stress in A335 P12 steel welds before and after stress-relaxation annealing through instrumented indentation technique,” Scripta Materialia 48 (2003) 743-748; JANG, “Estimation of residual stress by instrumented indentation: A review,” Journal of Ceramic Processing Research, Vol. 10, No. 3, 391-400 (2009); PONSLET et al., “Residual Stress Measurement Using The Hole Drilling Method And Laser Speckle Interferometry Part III: Analysis Technique,” Experimental Techniques, September/October 2003; 45-48; SURESH et al., “A New Method For Estimating Residual Stresses By Instrumented Sharp Indentation,” Acta Materialia, Vol. 46, No. 16, 5755-5767; Vishay Precision Group, “Measurement of Residual Stresses by the Hole-Drilling Strain Gage Method,” Tech Note TN-503, document number: 11053; revision: Nov. 1, 2010; www.micromeasurements.com; 19-33; XU et al., “Chapter 7: Residual Stress Determination Using Nanoindentation Technique,” Micro and Nano Mechanical Testing of Materials and Devices; Editors: Yang et al.; Springer Science+Business Media, LLC, 2008; doi: 10.1007/978-0-387-78701-5, 139-153; XU, “Estimation of residual stresses from elastic recovery of nanoindentation,” Philosophical Magazine, Vol. 86, No. 19, Jul. 1, 2006, 2835-2846; XU et al., “Influence of equi-biaxial residual stress on unloading behaviour of nanoindentation,” Acta Materialia, 53, (2005) 1913-1919, each of which is incorporated herein by reference in its entirety.
Some patents and patent publications discussing various aspects of measurement of residual stresses and/or indentation include U.S. Pat. No. 6,155,104 (Suresh et al.); U.S. Pat. No. 6,311,135 (Suresh et al.); U.S. Pat. No. 6,568,250 (Sinha); U.S. Pat. No. 6,851,300 (Kwon et al.); U.S. Pat. No. 7,472,603 (Kim et al.), U.S. Pat. Appl. Pub. Nos. 2007/0180924 (Warren et al.), 2007/0227236 (Bonilla et al.), 2010/0064765 (Han et al.), 2010/0108884 (Lou et al.), and Int'l PCT Pat. Appl. Pub. Nos. WO 2006/071001 (Kim) and WO 2008/096914 (Han), each of which is incorporated herein by reference in its entirety.
All patents and patent applications (e.g., from the United States or elsewhere) and all other published documents mentioned anywhere in this application are incorporated herein by reference, each in its entirety, as if fully reproduced herein.
Without limiting the scope of the present disclosure, a brief summary of some of the claimed embodiments is set forth below. Additional details of the summarized embodiments and/or additional embodiments of the present disclosure may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. § 1.72. The abstract is not intended to be used for interpreting the scope of the claims.